Acute myocardial infarctions are the result of partial or complete blockage of one or more coronary arteries, in which the blockage causes an undesired reduced diameter in the bodily vessel. Percutaneous treatment of acute myocardial infarctions may include the delivery and placement of a stent at the site of the blockage. Treating bodily conduits that have an undesired reduced diameter by means of a radially expandable tubular implant with a cutout or open meshed structure, currently called a “stent,” is known. This device may be introduced in an unexpanded/contracted state into the conduit to be treated and delivered to the area of the conduit that has an undesired reduced diameter. The device is then radially expanded, particularly by means of an inflatable balloon, or, when it has a self-expandable structure, the stent may be released from a sheath that contains the stent in its contracted state. With self-expanding stents in particular, the self-expansion of the stent further ensures that there is continuous radial force anchoring the stent in place.
Various stents are available to treat bodily lumens having an undesired reduced diameter, including balloon-expandable stents and self-expanding stents. These stents typically have a weaved open mesh that forms the outer wall of the stent.
Although a stent may be used to treat an undesired reduced diameter of a bodily conduit, the open mesh structure of the stent, when formed of a plurality of cells defining small openings, may reduce the stent's utility for bifurcation stenting. For example, a stent with a cell size that defines a small opening may obstruct access to a side branch. However, the use of a stent with cells having larger openings may reduce the structural integrity of the stent. Further, many stents lack the ability to capture and prevent thrombi from traveling through the patient's vascular system due to the cutout and open meshed structure of the stents. See “Comparison of Drug-Eluting Stent Cell Size Using Micro-CT: Important Data for Bifurcation Stent Selection,” EuroIntervention, 2008; vol. 4, pp 391-396.
In addition, a stent itself may cause problems over time, such as causing thrombosis formation (e.g., clots) within a blood vessel. For example, during bifurcation stenting with a stent having small cell openings, struts that are not in contact with the vessel wall may cause thrombosis formation.
The inability to capture and prevent thrombi from traveling through the patient's vascular system is particularly relevant with drug eluting stents, e.g., stents that elute anti-restenotic drugs from a polymer coating. The polymer coating on these stents may be responsible for late stent thrombosis when the stent is not well apposed to the vessel wall. Although such issues could be reduced by bioresorbable stents, the effective treatment of body lumens that have an undesired reduced diameter remains difficult because of an inability to capture and prevent passage of particles such as blood clots/thrombi after placement of the stent.
Abbott Laboratories' Vision stent has an open mesh outer wall that includes cells having an area of approximately 1.1271 mm2 and a relatively large opening when the stent is expanded to a 3.0 mm diameter (the diameter of a nominal blood vessel in which the stent may be used). Cells with such openings may be too large for effectively capturing smaller thrombi, while simultaneously blocking side branches more than is desirable.
Other known stents that have smaller cell sizes suffer even more from the inability to allow adequate blood flow to side branches because of the small cell size. For example, Boston Scientifics' Liberté stent has an open mesh outer wall that includes cells having an area of 0.5339 mm2 when the stent is expanded to a 3.0 mm diameter and smaller openings than the Vision stent that may not be capable of providing desirable levels of side branch access while still not providing desired thrombus protection.
Accordingly there remains a demand for devices and methods for effectively treating bodily conduits, particularly branched conduits, that have an undesired reduced diameter.